The present invention relates to exhaust gas recirculation systems for controlling the amount of exhaust gas recirculation in an engine.
Systems have recently been proposed which are designed to electrically compute and control the amount of exhaust gas recirculation (EGR). For example, the inventor, etc., have proposed a system in which the desired amount (ratio) of EGR is computed by an electronic control circuit such as a microcomputer, which receives an engine intake vacuum signal and engine rotational speed signal as its main input signals. However, the system has been found disadvantageous in that the opening and closing of the intake and exhaust valves of an engine result in intake air pulsations causing intake vacuum pulsations and moreover electric noise is caused by a sparking high voltage supplied to the spark plugs, thus causing the output of the electronic control circuit or the data indicative of the EGR quantity (i.e., the EGR ratio) to vary in response to the pulsations or the electric noise and thereby causing such engine troubles as unstable engine rotation or the like.